Method of treating insulated electrical conductors



Feb. 28, 1939..

S. E. BRILLHART METHOD OF TREATING INSULATED ELECTRICAL CONDUCTORS FiledDec. 31, 1935 W INVENTOI? 5. E. BRILL/$41??? Patented Feb. 28, 1939PATENT OFFICE METHOD OF TREATING INSULATED ELEC- TRICAL CONDUCTORSSamuel E. Brillhart,

Western Electric C Baltimore, Md., assignor to ompany, Incorporated, New

York, N. Y., a corporation 01 New York Application December 31, 1935,Serial No. 56,952

2 Claims.

This invention relates to a method of treating insulated electricalconductors and more particularly to a method of applying a coating ofwaxy substance such as mixtures comprising paraflln, carnauba wax,beeswax, and the like to the sheaths of insulated electrical conductors.

There are situations of various kinds in which it may be advantageous tohave the outer surfaces of insulated electrical conductors of a smoothand substantially frictionless nature. Thus if a plurality of strandshaving metallic conductive cores and insulating sheaths of rubbercompounds or the like to be combined in a cable, and such a cable bewound or bent in arcs of small radius relatively to the overall diameterof the cable, it is well that a certain amount of sliding of the strandsover each other be permitted, as such action will increase theflexibility of the cable as a whole and will decrease the liability tobreakage of strands on the outer side of the are of bending. However, ifthe rubber sheaths are in their natural state, the extremely highfrictional resistance to the sliding of one sheath over another willhinder if not prohibit such sliding. Another example is illustrated bythe case of an insulated conductor or cable having an outer cover ofserved or braided textile threads, where it is desired to draw a lengthof such cable into a preformed rigid conduit which may or may notcontain other conductors or cables already in situ therein, and in whichthe frictional resistance of the conductor or cable cover, especiallywhen braided, may rise to practically prohibitive values. In either suchinstance, the application of a thin film of waxy material such asparaifin, carnauba wax, beeswax, and the like, will obviate theaimculty. In some cases such films have been applied by passing theinsulated conductor or cable through a bath of hot molten wax. However,in some instances the subjection of insulated conductors or cables,especially such as include a sheath of rubber material, to a hot liquidmay have objectionable effects on the insulation.

An object of the present invention is to provide a method of applying acoating of waxy material to insulated electrical conductors withoutnecessitating the use of hot materials.

One embodiment of the invention contemplates the use of waxy material,such as paraffin, carnauba wax, beeswax and the like emulsified in awatery medium; this to be applied to the surface of an insulatedconductor or cable by dipping, spraying or in any other suitable manner,after which the coated conductor or cable is to be dried in any suitablemanner.

Other features and objects of the invention will appear from thefollowing detailed description of one embodiment thereof taken inconnection with the accompanying drawing in which the same referencenumerals are applied to identical parts in the several figures and inwhich Fig. 1 is a schematic diagram of an apparatus for carrying out themethod of the invention, and

Fig. 2 is a similar representation of a modified apparatus.

In the embodiment of the invention represented in Fig. 1, an insulatedconductor or cable Ill to be provided with a thin film of waxy substanceon its outer surface, is drawn from a supply reel l I, passed throughthe apparatus and wound on a take-up reel l2. A tank or vat 20 holds abath of an emulsion, in water, of parafiin, carnauba wax, beeswax, orthe like. The conductor H) passes over a guide sheave 21 above the tank,under a guide sheave or roller 22 submerged in the bath in the tank, andup over a guide sheave 23 to a wiper die 30. The die 30 serves merely toremove any excess of emulsion adherent to the conductor. After leavingthe die, the conductor may be passed through a drier generally indicatedat 40. This drier may be of any suitable construction, and is here shownas a tubular housing 4| of iron, ceramic material or other appropriatesubstance, housing a helical heating coil 42 supplied with electriccurrent from a source not shown, and through which the conductor passesaxially. From the drier 40, the treated conductor passes to the take-upreel I2. The drier may have guide sheaves 43 and 44.

Each of the units comprising the apparatus is of familiar constructionand operation, well known to those skilled in the art, and so is nothere described in detail.

In the embodiment disclosed in Fig. 2, the emulsion applying tank 20 andsheave 22 of Fig; l are replaced by a device to. spray the emulsion onthe conductor ID. This may be a vertical double walled cylinder 24,shown in section, having a plurality of perforations in the inner wall.The conductor l0 passes axially through the cylinder. The annularchamber between the walls of the .cylinder may then be supplied withemulsion under pressure from a source not shown through an inlet pipe25, and thus the emulsion is sprayed through the perforations upon theconductor.

It is found that the use of the emulsion permits the application of athinner and more uniform coating than do the customary methods of application using hot baths of molten wax material. The emulsion in waterand its vapors are totally noninflammable as contrasted with solutionsof waxes in various organic solvents heretofore used for such purposes;and there is no costly, difficult and possibly dangerous solventrecovery problem, or health protection problem as water is not worthrecovering and it and its vapors are not injurious to health. Also byapplying the emulsion cold there is less danger of injuriously affectingthe insulating material to which it is applied.

Also it is found that where colored coatings are desired it is possibleto add either or both pigments and dyes to the emulsion before it isapplied and so to obtain satisfactory colored films on the conductors.

Suitable emulsions of paraffin wax in water, as also of other waxes in awatery carrier, are available commercially on the open market under avariety of trade names. It is therefore not thought necessary todescribe the manufacture of such emulsions here, as this is no part ofthe present invention. Sufiice it to say that commercial emulsionscarrying up to 20% of paraflin dispersed in water have been foundsatisfactory in practicing the method of the present invention.

The method of the invention is not limited to the apparatus or devicesherein disclosed for carrying out the method, the principalcharacterizing feature of the invention being the use of an emulsion ofwaxy material in a watery carrier to apply a thin film of wax to theinsulating sheath of an electrical conductor or cable. Thus in someinstances it my be sufficient merely to dip the coiled conductor orcable in a vat of the emulsion, drain the conductor and let it dry atroom temperature, The wiper die may in some cases be dispensed with, orin other cases may be replaced by a wad of cotton, felt pads, compressedrubber wipers, air jets, or the like. The drier may in some instances beomitted, or may be externally heated as by gas flames (there being nofire hazard), or otherwise.

In the case of a multiconductor cable having a plurality of individualconductors each having an individual insulating sheath of material suchas a rubber compound characterized by a high frictional property, eachsuch rubber insulated strand may profitably be coated with a thin filmof waxy lubricant before the strands are assembled together in the coreof the cable. A cable thus manufactured will have greater flexibilitythan otherwise and will be less subject to rupture of individualconductor strands when coiled or bent, since the lubricated strands willslide easily over each other.

Where conductors or multiconductor cables are to be installed inconduits or the like by being pulled into them, and the conductors orcables have textile covers, especially such as are braided, the methodof the present invention may also be profitably applied to provide thetextile sheath with a thin, non-sticky film of waxy lubricant, renderingit easier to pull the cable into a conduit and serving to protect thetextile sheath against frictional abrasion.

The embodiment of the invention herein disclosed is illustrative onlyand may be departed from and modified in many ways without departingfrom the scope and spirit of the invention as pointed out in and limitedonly by the appended claims,

What is claimed is:

1. A method of treating a rubber sheathed electrical conductor whichcomprises the steps of applying to the surface of the sheath 9. quantityof an emulsion of paraffin in water, removing the excess of emulsionfrom the surface, and drying out the moisture from the emulsionremaining on the surface to leave a thin film of paraffin on the surfaceof the rubber sheath, the application of the emulsion and the removal ofexcess being carried out cold so that there is minimum absorption ofparaffin by the rubber.

2. A method of treating a rubber sheathed electrical conductor whichcomprises the steps of spraying on the surface of the sheath a quantityof an emulsion of paraffin in water, removing the excess of emulsionfrom the surface, and drying out the moisture from the emulsionremaining on the surface to leave a thin film of paraffin on the surfaceof the rubber sheath, the spraying on of the emulsion and the removal ofexcess being carried out cold so that there is minimum absorption ofparaffin by the rubber.

SAMUEL E. BRILLHART.

